Which principle or rule restricts from having more than two electrons in a single orbital?

Which of the following resonance structures is the most stable:

More highly repetitive DNA is found in heterochromatin than in euchromatin. 

Which of the following is not a telomeric function?

___________________ are inherited blood disorders resulting from abnormal hemoglobin that comes from a mutation that reduces or prevents synthesis of either α- or β-globin genes.

Genes that are expressed only in specific cell types are known as:

Which molecule is expected to have the greatest dipole moment?

A closed reading frame:

Repetitive DNA is invariably noncoding DNA.

Repetitive noncoding DNA makes up approximately what percentage of the human genome?